MosaicEditor image features

[campagnola]

Would like to see several features added to MosaicEditor image handling:

• Flexible/customizable filters to replace the fixed set of filter buttons (max/mean/edge/etc). User can add any number of "preset" buttons for single-click filter changes. In progress here: Image analysis #8
• Button to enable / disable auto gain control while moving time slider. Can we use the camera module's code for this? (and can it be implemented in pyqtgraph instead of acq4?)
• Quick control for disabling filter (maybe a check by the filter groupbox title)
• Option to apply settings to a selection of images (adjust levels / LUT, set filter, etc.)
• Option to link z-axes across images (depends on Record image transform for every frame in a recording. #2)
• Remember last used levels / LUT / filter (but remember initially recorded values as well?)
• Mask painting - user can manually paint masked areas over regions of a stack to facilitate 2D projection (for example, to make a 2D morphology image from a z-stack where fine dendrites are not visible in a max-projected image)